A research team led by Professor Hyun-Wook Lee at UNIST, in collaboration with KAIST and the University of Texas at Austin, has achieved a major breakthrough in improving the lifespan of iron-chromium redox flow batteries (Fe-Cr RFBs).
These large-scale, explosion-proof energy storage systems offer a safer and scalable solution for storing intermittent renewable energy such as wind and solar.
The team identified the root cause of performance degradation – a ligand exchange reaction involving hexacyanochromate – and developed an optimised electrolyte formulation to suppress it. By adjusting the cyanide-to-hydroxide ion ratio, the new formulation maintained stable capacity and efficiency over more than 250 charge-discharge cycles.
Unlike conventional batteries, flow batteries store energy in liquid electrolytes circulated by pumps, allowing for flexible scaling and enhanced safety. The use of water-based electrolytes eliminates explosion risks and makes Fe-Cr RFBs particularly suitable for grid-scale applications.
“This work demonstrates the potential to develop high-performance, long-lasting flow batteries using cost-effective iron-chromium electrolytes,” said Professor Lee. “Such technology is especially promising for countries with abundant renewable resources and large land areas, like China and European nations, seeking scalable energy storage solutions.”
While vanadium flow batteries remain closer to commercialisation, their cost and supply constraints limit widespread adoption. This advancement positions iron-chromium systems as a viable alternative for affordable, long-duration energy storage.
The findings were published online in the chemistry journal Angewandte Chemie International Edition.
